1) Field
Embodiments of the present invention generally relate to plasma processing equipment, and more particularly to methods of electrostatically clamping and declamping of a resistive substrate to a chuck disposed within a plasma processing chamber.
2) Description of Related Art
In a plasma processing chamber, such as a plasma etch chamber, the temperature of the substrate is often an important parameter to control during a process. A temperature of a substrate may be controlled by adjusting the temperature of a substrate holder, commonly called a chuck or pedestal. A heat sink and/or heat source is coupled to the chuck to control the chuck at a desired temperature. An electrostatic clamping force may be established between the substrate and the chuck to provide good thermal conduction between the substrate and the chuck (required for the substrate temperature control). One type of electrostatic chuck (ESC) utilizes the Johnson-Raybeck (JR) effect to clamp the substrate to the chuck.
Three dimensional IC (3DIC) manufacture is being adopted as a means to further increase IC integration and generally involves the stacking of multiple semiconductor substrates together, each substrate having a device layer thereon. For improved device cooling and simpler through silicon via (TSV) processing, a semiconductor substrate that is to be stacked upon another is thinned to 50 μm or less. At such thicknesses, the semiconductor substrate is no longer mechanically rigid enough to be safely handled by plasma processing equipment. The thinned semiconductor substrate is therefore affixed to a handle or carrier substrate prior to plasma processing. Currently, the preferred carrier substrate material is borosilicate glass, such as Corning 7740, offering the advantages of a coefficient of thermal expansion (CTE) that is well matched with that of silicon and relatively broad UV transparency window which facilitates affixing the thinned semiconductor substrate to the carrier substrate with UV-sensitive adhesives to form a multi-layered workpiece typically referred to as a silicon-on-glass (SiOG) substrate.
While ESCs have been in service for n-type or p-type silicon substrates conventional in integrated circuit (IC) processing, its functioning with substrates like SiOG which have an effective resistivity much higher than that of silicon, might be problematic causing chucking (resist reticulation, etc.) and dechucking (substrate sticking, etc.) failures.